# On the logarithmic bipartite fidelity of the open XXZ spin chain at $\Delta=-1/2$

### Submission summary

 As Contributors: Christian Hagendorf · Gilles Parez Arxiv Link: https://arxiv.org/abs/2111.15223v1 (pdf) Date submitted: 2022-01-03 11:19 Submitted by: Hagendorf, Christian Submitted to: SciPost Physics Academic field: Physics Specialties: Mathematical Physics Quantum Physics Statistical and Soft Matter Physics Approach: Theoretical

### Abstract

The open XXZ spin chain with the anisotropy $\Delta=-\frac12$ and a one-parameter family of diagonal boundary fields is studied at finite length. A determinant formula for an overlap involving the spin chain's ground-state vectors for different lengths is found. The overlap allows one to obtain an exact finite-size formula for the ground state's logarithmic bipartite fidelity. The leading terms of its asymptotic series for large chain lengths are evaluated. Their expressions confirm the predictions of conformal field theory for the fidelity.

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